Window coverings such as curtains, draperies and shade and blinds have been widely used in households and office environments. The opening (hoisting) and closing (extending) of the curtains mostly are done by pulling cords. This type of operation generally is adapted for Venetian blinds or curtains composed of a left and a right panel, but is not adaptable for one piece hoisting shade or curtain. Moreover, in conventional curtain hoisting clutch systems, when the cord is pulled bias to the right and then straightened again, the curtain will be fully extended. Pull the cord bias to the right again, the cord will be halted and the curtain will be rolled to the top end. Such clutch systems can either fully extend the curtain or completely roll the curtain, but cannot control the rolling of the curtain to any desired elevation. Hence their applications are limited.